Open AccessActive Efflux of the Free Acid form of the Fluorescent Dye 2′,7′‐Bis(2‐Carboxyethyl)‐5(6)‐Carboxyfluorescein in Multidrug‐Resistance‐Protein‐Overexpressing Murine and Human Leukemia Cells
Author(s) -
Draper Michael P.,
Martell Robin L.,
Levy Stuart B.
Publication year - 1997
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1997.0219a.x
Subject(s) - fluorescence , efflux , multiple drug resistance , leukemia , chemistry , fluorescent staining , biochemistry , microbiology and biotechnology , biology , immunology , staining , genetics , physics , quantum mechanics , antibiotics
Murine and human cell lines overexpressing the multidrug‐resistance protein (MRP) showed a marked decreased accumulation of the fluorescent dye 2′,7′‐bis(2‐carboxyethyl)‐5(6)‐carboxyfluorescein (BCECF). In contrast, less altered accumulation was seen in the P‐glycoprotein(P‐gp)‐overexpressing cell lines. The decreased drug accumulation was reversed by the energy inhibitors sodium azideI2‐deoxyglu‐cose and by the vinca alkaloid, vincristine, but not by the chemotherapeutic agents, etoposide and adriamycin. Decreased accumulation was linked to active efflux of the hydrophilic free acid form of BCECF from the MRP‐overexpressing cell lines, indicating that dye extrusion occurs after the dye ester has been converted to the free acid form in the cytoplasm. The finding suggests that MRP mediates removal of substrates from a cytoplasmic location. Buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, decreased the vincristine and etoposide resistance displayed by the MRP‐expressing murine cell lines, but did not affect the accumulation of BCECF. Thus, while glutathione may be involved in MRP‐mediated resistance to some chemotherapeutic agents, it is not necessary for efflux of substrates such as BCECF.